Wide-span pattern generator

ABSTRACT

A method and apparatus for positioning at least one terminal point of the scan of a medium by a beam is disclosed. The beam is moved in the direction of the scan from one point past a fiducial point having a known position with respect to the medium. There is registered a quantity related to the distance the beam moved from one point to the fiducial point. Thereafter, during scans of the medium, the one terminal point is shifted along the direction of the scan by a distance related to the registered quantity.

United States Patent [72] Inventor Solomon Manber 3,225,137 12/1965Johnson 178/6.7 Sands Poinl- 3,221,337 11/1965 Quinn et a1 4. 346/110 11 pp N9 8111474 3.195.113 7/1965 Giordano 340/173 1 Filed Mar-28-19692.903.598 9/1959 250/217 [45] Patented Nov. 16, 1971 FOREIGN PATENTS[73] Assignee Alphanumeric Incorporated 140 792 Lake 8 30,296 3/1966Canada a Primary Examiner-Kathleen H1 Clafi'y Assistant [:xaminer-ThomasDAmico [54] WIDE SPAN PATTERN GENERATOR Anomey camil p s i 11 Claims, 3Drawing Figs.

[52] U.S.Cl 178/15,

315/21- 346/ 1 10 ABSTRACT: A method and apparatus for positioning atleast 51 1111. C1 1. 1104115/34 one terminal point of the scan of; meyraflb mr s Field Sealdl 178/45v Closed The heam is moved in thedirection of the scan from 340/3241 172-5; 315/211 346/1 10 one pointpast a fiducial point having a known position with respect to themedium. There is registered a quantity related [56] References Cited tothe distance the beam moved from one point to the fiducial UNITED STATESPATENTS point. Thereafter, during scans of the medium, the one ter-3,447.026 5/1969 Townsend 315/21 mina] point is shifted along thedirection of the scan by 21 3,313,883 4/1967 Huntley... 178/15 distancerelated to the registered quantity.

FILM CARTRIDGE AMPLIFIER p p PHOTOCELL a; m pcs KNIFE EDGE g SiPfi sw BLENS MIRROR y s POSITIONER 0 R CRT HDS \ CRT CIRCUITS 1vos HORIZ DEF-LVERT DEFL INTENSITY ML MR AMP HDA V55 AMP LD A CONTROL 5 HP$4 t vs f-ITHORIZ POSITION vs VERTICAL STROKE GENERATOR HPg GENERATOR VSG I ETPAIENTEDIIIII Is IIIII SHEET 1 BF 2 I FILM CARTRIDGE AMPLIFIER T p p IPHOTOCELL 53 pcs i KNIFE EDGE 5 E ROTATABLE MIRROR 3 MIRROR P5 sw 2SMIRROR POsITIONER HDS [C5 CRT CIRCUITS CRC f -wos HORIZ. DEFL. vERT.DEFL. INTENSITY ML AMP. HDA V55 AMP. VDA CONTROL g MR HP54 L f vs F-ITHORIZI POSITION /EVS VERTICAL STROKE GENERATOR I-IPG GENERATOR vsG ET Po-; T PVO COMPUTER C F FILM CARTRIDGE INVENTOR Solomon Manber A TORNEYPATENTEDNIIII T FROM COMPUTER DEFL.

SHEET 2 [IF 2 VBS TO VERT.

AM P.

HORIZONTAL POsITION GENERATOR ET FRO I /PS FROM COM UTER PI-IOTOGELL TM7 AMPLIFIER PAMP AMP B DELAY 7A1 2 A GATE 1% 253 B Q R O EI\FFRO TM/ PsFLIP- OR 1 FLOP CIRCUIT DF TM FLOP CLOCK SFi 8 FR .CLK ML MR FFL1 V I\TM FFLO MRI 7 I V Y I GATE GATE ICOUNTER GOuNTER Q 54 TM TM T l 9 KLNL2 KR KRN FFR1 \MLI I GATEs GATEs VFROM vERTIcAL FFL1 STROKE GENERATOR/FFR1 N GATEs GATES G6 I 67 H G6 FROM GOMPuTER GP N cflN/i G2N FHO M Q IsuBTRAcTOR HORIZONTAL g D sue C O POSITION REG HPR 6 M58 GATEs Q /HPRN vFGON HORIZONTAL DIG. TO cORREGTION DIG|TAl TO ANALOG. cONvERTER ANALOGCONVERTER EPA J1EE To MIRROR ANALOG ADDER POsITIONER P AA HDAS CDAS ORCIRCUITS B2 (tHPs TO HORIZONTAL DEFL. AMP HDA WIDE SPAN PATTERNGENERATOR This invention pertains to pattern generators and moreparticularly to pattern generators for recording symbols on a wide spanrecord medium.

Within the past few years there has become available graphic artsquality pattern generators of the type using a cathode-ray tube whoseimage is projected onto a record medium such as photographic film. Thecharacters are built up of varying length parallel vertical strokeswhich abut each other in a horizontal direction. A typical patterngenerator of this type is shown in US. Pat. No. 3,305,841. ln order toob tain high-quality patterns, the cathode-ray tube should have aresolution of greater than 700 line pairs per inch and must have aminimum of distortion. These requirements limit the diameter of thecathode-ray tube and consequently the width dimension of record medium.Magnifying optical systems for increasing the width dimension of thecathode-ray tube image scan of the record medium can only double thewidth for all practical purposes. A mere doubling of the width cannotsatisfy many of the present requirements of the printing industry. Anexample will make the point clear. Present high-quality and economicallyrealistic cathode-ray tubes of the type herein required have only apractical scan width of about four inches. A practical and economicallyfeasible magnification is 2-to- 1. Thus the cathode-ray tubes scan iseffectively about eight inches. Therefore, it is possible to print onrecord mediums having an eight inch width. Such a width is suitable forprinting of many conventional size books and the like. However, manymagazines, newspapers and other books have greater page widths.

A solution to the problem is to use one optical path to scan the leftside of the record medium for writing the characters or symbols for thatside and to use another optical path to scan and write on the right sideof the record medium. It is possible to use two cathode-ray tubes witheach focused at one half of the record medium. A more economic solutionis to use one cathode-ray tube with a rotatable mirror or other opticalmeans to alternately project the image of the cathode-ray tube first toleft half of the record medium while the left half of a line of symbolsis written, and, then, to the right half of the record medium while theright half of same line of symbols is written. With either scheme thereis a change of the optical paths somewhere around the midpoint of theline of recorded symbols.

This transition of optical paths can create registration problems. Therewill be a misregistration of the right end of the scan via the leftoptical path with the left end of the scan via the right optical path,the adjacent terminal points of the scans. If this misregistration isslight and occurs in the space between symbols it may not be noticeableto the human eye. However, it is more likely that the transition willoccur while a symbol is being written. Such misregistration will causepartial overlap of portions of the symbol or an intrasymbol gap. Bothphenomena are noticeable upon visual inspection. In fact, since thesemisregistrations occur in each line, there is a sub jectivemagnification of the misregistration. It should be noted that evenslight misregistration will be apparent when it is realized thecathode-ray tube generates lines in the order of a thousandth of an inchin width.

Because of these very fine widths it is virtually impossible from apractical point of view to align precisely the two optical paths and tomaintain this alignment over an extended period of time. Therefore,exact mechanical alignments are not a solution to the problem.

lt is accordingly an object of the invention to provide a practicalreliable and automatic solution to the above-stated problem.

Briefly, the invention is directed to registering the adjacent terminalpoints of at least two adjacent scans of a record medium by a recordingbeam which scans a first portion of the record medium via a first pathand scans a second portion of the record medium via a second path. Thisis accomplished by having a fiducial point which is related to anintermediate point of the two adjacent partial scans, for example apoint where the transition from one scan to the other should occur whenthe record medium is scanned. A first partial scan, via the first path,is performed by the recoding beam past the fiducial point and there isregistered a first parameter related to the position of this scan whenthe recording beam is detected crossing the fiducial point. A secondpartial scan, via the second path, is performed by the recording beampast the fiducial point and there is registered a second parameterrelated to the position of this second scan when the recording beam isdetected crossing the fiducial point. The terminal point of one of theadjacent scans is then displaced by a distance related to the differenceof the two registered parameters.

Other objects, the features and advantageous of the invention will beapparent from the following detailed description when read with theaccompanying drawings which show by way of example presently preferredapparatus for practicing the invention.

In the drawing:

FIG. 1 shows, primarily in block diagram form, a cathoderay tube patterngenerator system for recording symbols on a record medium;

FIG. 2 is a partial view of the record medium plane as seen by thecathode-ray tube; and

F 16. 3 is a block diagram of the horizontal position generator of thesystem of FIG. 1.

For the sake of simplicity, several conventions will be used. The signallines which interconnect the units will bear the same reference numeralas the name of the signals and the signal name and signal line referencenumeral may be used interchangeably. For example, the HPS signal istransmitted on the HPS signal line Generally, only signal flow will bedescribed. Therefore, a statement such as the HPS signal is transmittedfrom the horizontal position generator HPG to the horizontal deflectionamplifier HDA means that there is transmitted a signal on the HPS signalline which connects horizontal position generator HPS to horizontallydeflection amplifier HDA. Furthennore, some signal lines are actuallycables of lines and these are designated by double arrowhead lines andgenerally carry coded combinations of signals representing binarynumbers. See, for example, line HO which connects computer CF tohorizontal position generator HPS. In this vein, statements such as anumber is transmitted from one unit to another unit" means that thecoded combination of signals representing the number is transmitted.

The system of FIG. 1 records characters generated on the face of acathode-ray tube CRT by projecting their images onto a photographic filmFILM. During the generation of characters, the cathode-ray tube CRT isdriven to form a raster of short-height vertical strokes which arecentered on a horizontal diameter 10 on the face plate of thecathode-ray tube CRT. While this raster is generated, the electron beamof the cathode-ray tube CRT is turned on and off at particular times inthe stroke in accordance with numbers represented by coded combinationsof signals received by the vertical stroke generator VSG from thecomputer CP. At the end of each vertical stroke the electron beam isnon'nally deflected one increment in the horizontal direction and a newstoke is initiated.

Now, the screen S of the cathode-ray tube CRT is projected by an opticalsystem LENS onto the photographic film in a film cartridge having anopening or window W (FIG. 2). A horizontal line of the film at thewindow can be visualized as being a series of equispaced points alongone coordinate axis of a grid system wherein, say, the left-hand edge iscoordinate 0, the midpoint 8,191 and the right-hand edge 16,383 fornormal reader viewing. Therefore, any horizontal position on the filmcan be specified by a number. (It should be noted that these numbers aregiven by way of example and not limitation). The numbers from 0 to 8,191encompass the left half of the film and the numbers 8,192 to 16,383 theright half of the film. In addition, during the generation of patterns,the horizontal diameter 10 of the cathode-ray tube screen S (actuallyonly the central portion thereof, say, four inches of a five inchlength), can also be visualized as a series of such points with one endhaving a value and the other end the value 8,l9l. If it be assumed forthe sake of simplicity that there is no left/right inversions throughthe optical system, then the point 0 is 2 inches to the lefi of thecenter of the screen and the point 8,l9l is inches to the right of thecenter of the screen. It should be noted that there is still someavailable deflection to the lefl of the point 0 and to the right of thepoint 8,191. This extra deflection will be used in a test mode which ishereinafter described. However, for the present, it should be ignored.

The image of the screen of the cathode-ray tube is controliablyprojected onto either the lefi half of the film or the right half of thefilm. Thus each point on the horizontal diameter of the cathode-raytubes screen is related to one point on the right half of the film andone point on the left half of the film. For example, ideally, the point0 on the cathode-ray tube screen should project to either the point 0 onthe film or the point 8,l92 on the film. It is therefore, possible toaddress where any vertical stroke will be written on the film. Thehorizontal position generator HPG stores the numbers, one at a time,representing the desired address and generates two signals, onerepresenting the horizontal position of the beam of the cathode-ray tubeCRT and the other representing which of two optical paths will be usedto project the image of the screen onto the film.

With this in mind, the system comprises a computer CP which transmitsserially the numbers representing the lengths of the vertical strokesvia the signal lines V0 to the vertical stroke generator VSG. It canalso transmit numbers representing the horizontal position of a verticalstroke via the HO lines to the horizontal position generator HPG. Inaddition, it can transmit a calibrate test signal, via line T, to thehorizontal position generator HPG and receive therefrom an end of testsignal ET. The vertical stroke generator VSG can be considered toinclude means for generating the equivalent of a periodically recurringlinear sawtooth signal which is transmitted via line VS to verticaldeflection amplifier VDA, and means for emitting an EVS pulse at the endof each sawtooth signal. It also includes a counting register which unitincrements to increase the count in synchronism with the amplitude ofthe sawtooth signal; and a comparator for comparing the accumulatedcount with a number received from the V0 signal lines to generate ITsignals fed to intensity control IC for changing the state of theelectron beam of the cathode-ray tube CRT whenever an equality isdetected. Further details may be found in the above cited U.S. Pat. No.3,305,841. In addition, when it receives the test signal T from thecomparator it generates a signal which insures that the electron beam ison and no sawtooth is generated.

The intensity control IC can be a one stage binary counter which changesstate each time it receives an IT signal and transmits a signal via line[C8 to a suitable amplifier in the cathode-ray tube circuits CRC forcontrolling the control grid (Z-axis) of the cathode-ray tube CRT. Thevertical deflection amplifier VDA can be a suitable analog adder whichcan amplitude add the signal on line VS (the sawtooth wave form source)and the signal on line VBS (a signal of constant amplitude whenpresent). As a practical matter, only one of the signals is present atany given time, so that the adder can be considered as an analog ORcircuit. The output of the amplifier is fed via the VDS signal line tothe vertical deflection circuits of the cathode-ray tube assemblage.

The horizontal position generator HPG is used to control the horizontalpositioning of the image on the film. For the present, it can beconsidered to include a register which can be set to a given number andthe number can be unit incremented. The signals representing the storednumber are converted by a digital-to-analog converter to a signal whoseamplitude is a function of the stored number. This signal is fed via theHPS signal line to the horizontal deflection amplifier HDA. In addition,when the number stored in the register is greater than 8,19 l, thehorizontal position generator transmits an R signal to the mirrorpositioner MP. The details of horizontal position generator HPG will bedisclosed hereinafter with a description of FIG. 3.

The optical projection system LENS projects the image of the screen S ofthe cathode-ray tube CRT onto rotatable mirror RM. When mirror RM is inthe position shown the image is deflected, via mirror M1, to the lefthalf of the film. Mirror RM is rotated by mirror positioner MP, asuitable drive means which when it does not receive an R signal rotatesthe mirror to the position shown. In the presence of the R signal,mirror RM is in the alternate position. Ganged to the drive means is themoving contact of switch SW which follows the movement of the mirror RM.When the mirror RM is in a position to deflect to the right, a positivesignal passes via the moving contact from battery B to line MR. In thealternate position a positive signal is on line ML. (Although aschematicized mechanical means is shown, it should be apparent that inpractice suitable electronic switching and positioning circuits would beused.) The MR and mL signals are also fed to the computer GP to preventtransmission of stroke information when both signals are absent; i.e.,when the mirror is rotating.

The image of the horizontal diameter 10 of the screen S projects on thefilm within the writing window W of FIG. 2. The film can move within acartridge which has the window W that faces screen of the cathode-raytube CRT.

Positioned above the window W and facing the cathode-ray tube screen Sis a light detector 12 with an opening 14 substantially aligned with themidpoint of the film (see FIG. 2). In FIG. 1, there is shown that lightdetector 12 includes a photocell PC behind a knife edge KE. It isequally possible to narrow the opening 14 down to a fine vertical slitand dispense with the knife edge. In either event, whenever thephotocell PC is illuminated it emits a PCS signal to amplifier PAMPwhich transmits a pulse on the PS signal line.

A simple description of a writing mode for the recording of characterswill now be briefly given. Generally, the computer CP will transmit ahorizontal address number via the lines HO to the horizontal positiongenerator HPG. If this number is less than 8,191, no R signal isgenerated and the rotatable mirror RM is in the position indicated. Thescreen of the cathode-ray tube images on the left half of the film inthe window W and the beam of the cathode-ray tube is aimed at a point onthe screen S which is related to the horizontal address number stored inthe horizontal position generator HPG. (This number is converted to ananalog signal HPS whose amplitude represents the number). The I-IPSsignal is fed via the horizontal deflection amplifier I-IDA and the HDSsignal line to the cathode-ray tube circuits CRC where it is usedhorizontally to deflect the electron beam. The computer now transmitsvertical stroke length numbers to the vertical stroke generator VSG viathe V0 lines. Vertical stroke generator VSG now starts generating thevertical strokes by transmitting a recurring sawtooth signal via linesVS, vertical deflection amplifier VDA and line VDS to the CRT circuitsCRC. At the same time, generator VSG intensity modulates the electronbeam in accordance with the received stroke length numbers bytransmitting the IT signal to intensity control [C which in turntransmits ICS signals to CRT circuits CRC.

At the end of each vertical stroke, vertical stroke generator VSGtransmits an EVS pulse to the horizontal position generator I-IPG toincrement the number stored therein by one. For example, if the computerCP initially loaded the horizontal address number 96 in the register,the first vertical stroke will be at coordinate point 96 on the screen Sof the cathode-ray tube and recorded at coordinate point 96 OF THE FILM.After this first stroke, the EVS pulse increments the address to 97 andthe second vertical stroke is at coordinate point 97 on the screen andrecorded at coordinate point 97 of the film. This operation continuesuntil the horizontal address stored in the register of the horizontalposition generator HPG becomes 8,192. At that time the R signal is fedto the mirror positioner MP from the horizontal position generator HPG.Mirror RM is rotated to the position shown in dotted outline and thescreen image is projected onto the right half of the film. Thedigitalto-analog converter in the horizontal position generator l-IPGignores the most significant binary bit position of the register storingthe horizontal address number. Therefore, the HPS signal represents theumber zero. Hence, the vertical stroke for the number 8,192 will be atthe zero coordinate point on the screen S but will be recorded at the8,192 coordinate point on the film. The recording routine then continuesin the usual manner for numbers 8,193, When a line has been written, thefilm can be moved longitudinally one line up and a new line can berecorded.

There is an inherent source of registration error in the system asdescribed. It was tactily assumed, that coordinate point 8,191 on thescreen 8 was projected over the left mirror path to coordinate point8.191 on the film. Misalignment of the optical path'could' cause screencoordinates point 8,191 to be projected to a different coordinate pointeither greater or less than 8,191. Similarly, coordinate point zero onthe screen S could be projected via the right mirror path to acoordinate point on the film of greater or less than 8,192. Thereforesome method and means must be provided to test and compensate for suchpossible misregistration.

Generally, a test mode is periodically called for the computer CP. Inthe test mode, the computer CP suspends the transmission of strokeinformation to the vertical stroke generator VSG which no longergenerates the vertical strokes but leaves the electron beam in the onstate. The horizontal position generator generates a VBS signal which isfed to the vertical deflection amplifier VDA. This signal deflects theelectron beam up above the window W to a level where it will intersectthe opening 14 of the light detector 12 during horizontal scans.

The horizontal position generator HPG is preset to horizontally locatethe electron beam slightly to the left of the point 8,191 on the screenof the cathode-ray tube CRT with the left hand optical path operative(mirror RM projects light to mirror M l The beam is then incrementallydeflected to the right until it is sensed by light detector 12. A firstnumber related to the number of increments the beam had moved isregistered in the horizontal position generator l-IPG. The horizontalposition generator HPG is then preset to again horizontally locate theelectron beam slightly to the left of point zero on the screen but nowthe right-hand and optical path is operative because the R signal isforced to be present. The electron beam is again incrementally deflectedto the right until it is sensed by light detector 12. A second numberrelated to the number of increments the beam had now moved is alsoregistered in the horizontal position generator HPG. The second numberis subtracted from the first number and the difference, including thesign of the difference, is stored in the horizontal position generatorHPG. This signed difference is a measure of the horizontalmisregistration of the end of the left half horizontal scan and thestart of the right half horizontal scan of the window.

If it is decided that the left half scan is to remain fixed wherever itoccurs, then while the right half scan is being performed a signalcorrection voltage is superimposed on the normal horizontal deflectionvoltage. A negative correction voltage which is related to a negativedifi'erence number will shift the right half scan to the left by anamount proportional to the magnitude of the difference number. Apositive difference number will result in the generation of a positivecorrection voltage which will shift the right half scan to the right byan amount proportional to the magnitude of the difference number. Inthis way all misregistrations at the center of the line are removed.Although it is true that the result may be that the whole line isshifted either right or left. such shifts within the normally occuringdrift ranges are not noticeable since they are only detectable at theends of the line. The major portion of the circuitry for performing thetest and correction routine is in the horizontal position generatorl-IPG as shown in FIG. 3.

The details of the horizontal position generator l-IPG will be explainedfor the following description of the test and correction routine. Whenthe computer CP enters the test mode, it transmits a T signal to thevertical stroke generator VSG (FIG. 1) which stops generating thevertical strokes and causes the electron beam to remain on. Inparticular, no EVS signals are transmitted therefrom to the horizontalposition register. The T signal is also transmitted to the horizontalposition generator HPG where it is received by amplifier Al. The Boutput of amplifier Al starts transmitting the VHS signal to thevertical deflection amplifier VDA for upwardly deflecting the electronbeam to the level of the light detector 12 (see FIGS. 1 and 2). Thepositive output of amplifier Al now transmits a signal on the TM signalline. The TM signal is used in several places to indicate the test modeand is used in other places to initialize certain logical elements. Inparticular, the TM signal'isfed to the set terminal of flip-flop F F Land via OR circuit B1 to the reset terminal of flip-flop FFR. Each ofthe flip-flops is of the conventional set/reset type having capacitorinputs or the equivalent so that they switch on the leading edge of areceived signal. The TM signal is fed to the preset input C of countersKL and KR to preset the counters to the number -200. (The presettingoccurs on the leading edge of a received signal). Each of the countersis an up counter which adds 1 to the accumulated count each time itreceives a pulse at its unit input I. The counters also store a sign bitwhich is negative for the first two hundred increments and becomespositive thereafter. The accumulated count, in binary representation, iscontinuously available on a plurality of parallel output lines. The TMsignal alerts gates G1 and G2. These gates are parallel arrays ofconventional three-input AND-circuits one per output signal line of thecounters KL and KR, respectively. And the TM signal clears subtractorSUB to zero. Subtractor SUB can be a parallel binary subtractor registerwhich subtracts a number represented by signals received at subtrahendinputs S from a number represented by signals received at minuend inputsM and stores the difference for transmission from difference outputs D.The subtractor is algebraic in the sense that the subtraction processtakes into account the sign of the minuend and subtrahend numbers andtransmits a signed difference.

When flip-flop FFL was set it started transmitting an FFLl signal fromits 1" output. The leading edge of the FFLl signal is fed to CM presetinput of horizontal position register HPR. This register can be al4-stage binary up counter which can be forced set to given values bysignals received in parallel on the HO signal lines. In addition, it canbe set to the specific value of 8,191 by a signal received at the CMinput or to the specific value 8,192 by a signal received at the COinput. The counter is unit incremented by pulses received at the Iinput. The signals representing the binary count accumulated in thefirst l3 stages are transmitted to the HPRN signal lines. The signalrepresenting the state of the 14th stage (the most significant bit) istransmitted from the M88 output to the line R.

The FFLI signal opens gates G1 which has been altered by the TM signal.Finally, the FF Ll signal alerts gate G3, a threeinput AND-circuit.

Now, it should be recalled that horizontal position register HPR ispreset to the number 8,191. This number in binary form is a zero in themost-significant bit position and ones in the 13 following positions.Thus this number fed, via the HPRN signal lines, to the horizontaldigital-to-analog converter I-IDA which never receives the mostsignificant bit (it is only connected to the 13 lower counter states) isthe greatest number which it can possibly receive. Converter HDAtransmits an analog signal, of maximum amplitude, say, 8,191 units ofamplitude, via the HDAS signal line to the analog adder AA. Theamplitude of this signal is sufficient to position the electron beam tothe horizontal point 8,191 on the screen of the cathode-ray tube. Sincethe most significant bit is zero, there is no R signal at this time andthe rotating mirror RM (FIG. 1) deflects the image to mirror M1 and theleft optical path is operative. However, the electron beam is to theleft of point 8,191 on the screen because of the following action.

lt will be recalled teat counter KL had been preset to 200, the signalsrepresenting this number are transmitted via the KLN signal lines, thegates G1, the GlN signal lines, the OR circuits B2 (a parallel array ofthree-input OR-circuits) and the lines OCN to the correctiondigital-to-analog converter CDA. This converter is a signed converterwhich transmits a signal having an amplitude related to the magnitude ofthe received binary number and a polarity which corresponds to the signof the binary number. Accordingly, the signal on line CDAS is negativeand has an amplitude of 200 units. The signals on lines HDAS and CDASare algebraically amplitude added by analog adder AA which now transmitsa signal on line HPS of +7,99l units to the horizontal deflectionamplifier HDA (FlG. 1). in this manner the electron beam is positionedto the left of the opening 14 of the detector 12.

When tee rotating mirror RM reaches the left position, switch SW (MG. 1)starts generating the ML signal which opens gate G3. Pulses from clockCLK which can be a freerunning pulse generator, pass via gate G3 andline MLl to the increment input I of counter KL. For each pulse receivedthe accumulated count increases by one from the initial value of 200.Thus, the CDAS signal becomes less negative and the HPS signal morepositive. The net effect is that the electron beam start-moving towardthe right. This continues until the detector 112 senses the electronbeam. The amplifier RAMP connected to the photocell PC (FIG. 1) via thePCS signal line transmits a PS pulse signal to the reset input offlip-flop FF 1 which resets terminating the FFLl signal and initiatingthe F FLO signal.

The FFLO signal, fed to the set input of flip-flop FF R triggers theflip-flop to the set state causing the generating of the FF! signal. TheFFR! signal alerts gate G4, a three-input AND-circuit and opens gatesG2, previously alerted by the TM signal. In addition, the F FRI signalis fed to the CO input of horizontal position register HPR to reset theregister to the number 8,192. This number, in binary representation, hasa one in the most-significant-bit position and zeros in the 13 lower bitpositions. Therefore, a signal is present on the line R and no signalspresent on the HPRN signals lines. Accordingly, horizontal digital toanalog converter HDA transmits a zero amplitude signal on the line HDAS.This would normally position the electron beam to the zero point on thescreen of the cathode-ray tube. However, just as previously describedwith respect to the counter KL, the counter KR was also preset to 200,and, since the gates G2 are now open, the signals representing thisnumber are fed via the KRN lines, gate G2, the G2N lines, theOR-circuits B2 and the OCN lines to the correction digital-to-analogconverter CBA. The converter CDA transmits a negative signal having anamplitude 200 units on the CDAS line to analog adder AA. The result isthat analog adder AA transmits, via the HPS line to the horizontaldeflection amplifier HDA a negative signal of 200 units amplitude andthe electron beam is at a point 200 units to the left of the zero point.

At the same time, the R signal causes the repositioning of the rotatablemirror RM to deflect the image of the screen to mirror M2 (F IG. 1) andthe right optical path is operative with the electron beam to the leftof the opening 14 of detector 12. When mirror RM reaches the rightposition, switch SW starts transmitting the MR signal.

The MR signal opens the three-input AND-circuit G4 causing clock pulsesto pass from clock source CLK via the MRI line to the increment input Iof counter KR which starts unit incrementing up from -200. Just asdescribed for counter KL, the electron beam starts moving toward theright until it is sensed by detector i2 (HO. 1) and another PS pulse isgenerated. The PS pulse passes through OR circuit B1 to the reset inputof flip-flop FFR. Flip-flop FFR resets, terminating the FFRl signal andinitiating the FFRO signal. With the end of the F F RT signal, gate G4closes ending the incrementing of counter KR which now contains a signednumber related to the electron beams crossing of the detector 12 via theright optical path.

The leading edge of the FFRO signal passes via difierentiator DF throughgate G5, a two-input AND-circuit, to become the ET signal. Note thesecond input to gate G5 is the TM signal via delay D. The purpose ofdelay D and difi'erentiator DF is to insure that an ET pulse is onlygenerated after the occurrence of the second PS pulse and not at thestart of the test mode. The ET signal is fed back to the computer C? toend the test mode by terminating the T signal. The ET pulse signal alsostrobes gates G6 and G7, pluralities of two-input AND- circuits.

The signals representing the signed number in counter KL pass, via linesKLN, gates G6 and line G6N to the minuend input M of subtractor SUBwhile the signals representing the signed number in counter KR pass, vialines KRN, gates G7 and line G7N, to the subtrahend inputs S ofsubtractor SUB. Subtractor SUB algebraically subtracts the two numbersand stores the signed difference. This stored signed difference numberwill be used during the generate mode to horizontally shift the rightscan. To illustrate its operation, several examples will be given.

Example 1.

Assume that the test mode, counter KL ends up storing the count zero;i.e., NKL=O. This means the left scan would end exactly at point 819] onthe film. Assume also that counter KR ending up storing the count zero;i.e., NKR=0, then tee right scan would start exactly at point 8,l92 onthe film. The difference between the numbers NKL and NKR is also zeroand there would be no horizontal shifting of the right scan. Notewhenever NKL=NKR there is no shifting to the right scan.

EXAMPLE 2.

Assume NKL=-a negative number. This means that the left scan would endto the left of point 8,l9l on the film. Say NKL=I00, then the left scanwould end at point 8,09 I. Now several cases can arise. if NKR l00, thenthe right scan would start to the left of point 8,092 on the film andthere would be an overlap of scans. (Say, NKR =l50, then the right scanwould start at point 8,042. In these cases, the right scan must beshifted to the right. For example, if NKL =-l00 and NKR 50, then NKL NKR=+50 and the right scan is shifted 50 points to the right. Again if NKLis negative and NKR l00, then the right scan would start to the right ofpoint 8,092 and there would be a gap in the scans. in this case, theright scan must be shifted to the left. Assume N KL I00 and NKR =-50,then NKL NKR =-50 and the right scan is shifted 50 point to the left.

EXAMPLE 3.

if NKL is positive, then the left scan would end to the right of point8,19l. Assume NKL =+l00, then the left scan would end at point 8,291 onthe film. lf NKR NKL -HOO, then the right scan would start to the rightof point 8,292 and there would be a gap in the scan. Say NKR =+l50, thenthe right scan would start at point 8,342 on the film. Note: NKL NKR=+l00 (+l50) =50 and the right scan would be shifted 50 points to theleft. If NKR NKL =l-l00, then there would be an overlap of the scans.Assume NKR =50, then NKL NKR =+l00 (50) =0+l50 and the right scan wouldbe shifted points to the right.

There will now be described how the correction stored in subtractor SUBis used during the generate mode.

During the generate mode, computer CP transmits the starting point ofthe horizontal scan by transmitting the initial horizontal address, viathe HO signal lines to the horizontal position register HPR and thestroke length information via the V0 signal lines, to the vertical stokegenerator VSG (FIG. I). Note: at this time it will be assumed that thenumber in register HPR is less than 8,192. Therefore, the left opticalpath is operative because no R signal is generated. At the end of eachvertical stroke, generator VSG emits an EVS pulse which is fed to theincrement input 1 of horizontal position register HPR. The contents ofthis register are continuously convened to a horizontal deflectionsignal by converter MBA and fed via lines HDAS and analog adder AA toline HPS to deflect the beam one point to the right for each unitincrement. When the count reaches 8,192, the R signal is generated andthe right optical path becomes operative. it is now necessary to add acorrection it necessary. The R signal in addition to going to the mirrorpositioner MP is also fed to gates 68, a parallel array of two-inputAND-circuits. The signals representing the signed correction value passfrom the difference outputs D of subtractor SUB, via the SO lines, thegates G8, lines G8N, OR- circuits B2 and lines OCN to correctiondigital-to-analog converter CDA. The proper polarity correction signalis fed via lines CDAS to analog adder AA where it is algebraically addedto signal HDAS and the resulting signal transmitted via the l-lPS lineto the horizontal deflection amplifier HDA.

It should be noted that although the correction has been performed onlyfor the right scan, the system could be modified to perform correctionson the left scan or on both scans with respect to a fiducial point. Allof these variations come within the scope of the invention.

in addition, although only two optical paths were disclosed wherein eachpath recorded images on a different half of the record medium, theinvention contemplates a plurality of optical paths each of whichrecords images on a different fraction of the record medium.

Furthermore, although only a method of insuring horizontal registrationhas been described, a similar technique can be used for verticalregistration What is claims is:

l. The method of registering the adjacent tenninal points of at leasttwo longitudinally adjacent scans along the same line of anenergy-absorbing medium by a beam of energy by periodically measuringthe degree of longitudinal misregistration of the adjacent end points ofsaid longitudinally adjacent scans, recording a quantity related to themeasured degree of longitudinal misregistration, and shifting the startor end of at least one of said longitudinally adjacent scans by anamount related to the recorded quantity each time the saidlongitudinally adjacent scans are sequentially performed.

2. The method of recording a line of patterns on recording mediumcomprising the steps of generating the patterns form a single source,projecting a first portion of the line of patterns, via a first opticalpath, to a first half of the record medium, projecting a second portionof the line of patterns, via a second optical path, to a second half ofthe record medium, and displacing along the direction of said line theimages of the patterns projected via at least one of said optical pathsby a distance related to any possible misregistration, at thedemarcation of the halves of the record medium, of the images projectedthereon via the different optical paths.

3. The method of registering the adjacent terminal points of at leasttwo adjacent scans of a record medium by a recording beam which scans afirst portion of the record medium via a first path and scans a secondportion of the record medium via a second path comprising the stepsproviding a fiducial point related to an intermediate point of said twoadjacent partial scans, performing at least a first partial scan withsaid recording beam via said first path, registering a first parameterrelated to the position of said first partial scan when said recordingbeam is detected crossing said fiducial point, performing at least asecond partial scan with said recording beam, registering a secondparameter related to the position of said second partial scan when saidrecording beam is detected crossing said fiducial point, and displacingthe adjacent terminal of at least one of the two adjacent scans inaccordance with the difference of said parameters.

4. Apparatus for recording lines of patterns on a photosensitive mediumcomprising means for generating successive lines of patterns ofradiation, image projection means for sequentially projecting the firsthalf of each line onto one half of the photosensitive medium and thesecond half of each line onto the other half of the photosensitivemedium, means for sensing for possible misregistration of the patternsprojected on one half of the photosensitive medium with respect to thepatterns projected on the other half of the photosensitive medium, andmeans responsive to said sensing means for shifting in the direction ofsaid line the lines of patterns projected onto at least one-half of thephotosensitive medium.

5. The method of claim 2 wherein the image displacement is performed bydisplacing the position where the patterns are generated.

6. The apparatus of claim 4 wherein said generating means includes acathode-ray tube assemblage with a screen and electron beam deflectionmeans responsive to signals with the patterns being traced on the screenby the electron beam and said shifting means includes means forsuperimposing on the signals which deflect the electron beam in a givendirection related to the direction of the line of characters aconstant-amplitude signal during the generation of the lines of patternswhich are projected onto said one-half of the photosensitive medium.

7. The apparatus of claim 4 wherein said generating means is acathode-ray tube assemblage and said image projection means includes arotatable mirror.

8. The apparatus of claim 4 wherein said sensing means includes animage-sensing means having a given position with respect to saidphotosensitive medium, means for scanning an image from a startingposition past said image sensing means and means responsive to saidimage sensing means for registering a quantity related to the distancefrom said starting position to said given position.

9. Apparatus for recording a line of patterns on a photosensitive mediumcomprising a cathode ray tube assemblage having a screen and an electronbeam and including at least means for deflecting the electron beam in atleast one direction across the screen of the cathode-ray tube and meansfor intensity modulating the electron beam, optical projection means foralternately projecting the image of the screen of the cathodeway tubevia a first optical path onto the first half of the photosensitivemedium, or via a second optical path onto the second half of thephotosensitive medium, a photosensitive detector having a given positionwith respect to the width dimension of the photosensitive medium, testcontrol means operative on said deflecting means and said opticalprojection means for causing said deflecting means to deflect theelectron beam to scan at least once in said one direction starting froma given point on said screen and for causing said optical projectionmeans to project, via the first optical path, the image of the scan tomove past said photosensitive detector, means for registering a firstrepresentation of the distance between the starting point of the scanand the point where the scan is detected by said photosensitivedetector, means for generating a correction deflection signal having avalue re lated to said first representation registered by saidregistering means, and means for applying said correction deflectionsignal to said deflecting means when the image of said screen isprojected onto the photosensitive medium via a particular one of theoptical paths.

10. The apparatus of claim 10 wherein said test control means causes thedeflecting means to deflect the electron beam to scan at least a secondtime in said one direction starting from a given point and for causingsaid optical projecting means to project, via the second optical path,the image of the second scan to move past said photosensitive detector,said registering means further registering a second representation ofthe distance between the starting point of the second scan and the pointwhere the second scan is detected by said photosensitive detector, andsaid correction deflection signal generation means generates thecorrection deflection signal in accordance with the relative values ofsaid first and second representations.

11. The apparatus of claim 10 wherein the correction deflection signalhas an amplitude related to the difference between the values of thefirst and second representations.

1. The method of registering the adjacent terminal points of at leasttwo longitudinally adjacent scans along the same line of anenergy-absorbing medium by a beam of energy by periodically measuringthe degree of longitudinal misregistration of the adjacent end points ofsaid longitudinally adjacent scans, recording a quantity related to themeasured degree of longitudinal misregistration, and shifting the startor end of at least one of said longitudinally adjacent scans by anamount related to the recorded quantity each time the saidlongitudinally adjacent scans are sequentially performed.
 2. The methodof recording a line of patterns on recording medium comprising the stepsof generating the patterns form a single source, projecting a firstportion of the line of patterns, via a first optical path, to a firsthalf of the record medium, projecting a second portion of the line ofpatterns, via a second optical path, to a second half of the recordmedium, and displacing along the direction of said line the images ofthe patterns projected via at least one of said optical paths by adistance related to any possible misregistration, at the demarcation ofthe halves of the record medium, of the images projected thereon via thedifferent optical paths.
 3. The method of registering the adjacentterminal points of at least two adjacent scans of a record medium by arecording beam which scans a first portion of the record medium via afirst path and scans a second portion of the record medium via a secondpath comprising the steps providing a fiducial point related to anintermediate point of said two adjacent pArtial scans, performing atleast a first partial scan with said recording beam via said first path,registering a first parameter related to the position of said firstpartial scan when said recording beam is detected crossing said fiducialpoint, performing at least a second partial scan with said recordingbeam, registering a second parameter related to the position of saidsecond partial scan when said recording beam is detected crossing saidfiducial point, and displacing the adjacent terminal of at least one ofthe two adjacent scans in accordance with the difference of saidparameters.
 4. Apparatus for recording lines of patterns on aphotosensitive medium comprising means for generating successive linesof patterns of radiation, image projection means for sequentiallyprojecting the first half of each line onto one half of thephotosensitive medium and the second half of each line onto the otherhalf of the photosensitive medium, means for sensing for possiblemisregistration of the patterns projected on one half of thephotosensitive medium with respect to the patterns projected on theother half of the photosensitive medium, and means responsive to saidsensing means for shifting in the direction of said line the lines ofpatterns projected onto at least one-half of the photosensitive medium.5. The method of claim 2 wherein the image displacement is performed bydisplacing the position where the patterns are generated.
 6. Theapparatus of claim 4 wherein said generating means includes acathode-ray tube assemblage with a screen and electron beam deflectionmeans responsive to signals with the patterns being traced on the screenby the electron beam and said shifting means includes means forsuperimposing on the signals which deflect the electron beam in a givendirection related to the direction of the line of characters aconstant-amplitude signal during the generation of the lines of patternswhich are projected onto said one-half of the photosensitive medium. 7.The apparatus of claim 4 wherein said generating means is a cathode-raytube assemblage and said image projection means includes a rotatablemirror.
 8. The apparatus of claim 4 wherein said sensing means includesan image-sensing means having a given position with respect to saidphotosensitive medium, means for scanning an image from a startingposition past said image sensing means and means responsive to saidimage sensing means for registering a quantity related to the distancefrom said starting position to said given position.
 9. Apparatus forrecording a line of patterns on a photosensitive medium comprising acathode ray tube assemblage having a screen and an electron beam andincluding at least means for deflecting the electron beam in at leastone direction across the screen of the cathode-ray tube and means forintensity modulating the electron beam, optical projection means foralternately projecting the image of the screen of the cathode-ray tubevia a first optical path onto the first half of the photosensitivemedium, or via a second optical path onto the second half of thephotosensitive medium, a photosensitive detector having a given positionwith respect to the width dimension of the photosensitive medium, testcontrol means operative on said deflecting means and said opticalprojection means for causing said deflecting means to deflect theelectron beam to scan at least once in said one direction starting froma given point on said screen and for causing said optical projectionmeans to project, via the first optical path, the image of the scan tomove past said photosensitive detector, means for registering a firstrepresentation of the distance between the starting point of the scanand the point where the scan is detected by said photosensitivedetector, means for generating a correction deflection signal having avalue related to said first representation registered by saidregistering means, and means for applying said correction deflectionsignal to said deflecting Means when the image of said screen isprojected onto the photosensitive medium via a particular one of theoptical paths.
 10. The apparatus of claim 10 wherein said test controlmeans causes the deflecting means to deflect the electron beam to scanat least a second time in said one direction starting from a given pointand for causing said optical projecting means to project, via the secondoptical path, the image of the second scan to move past saidphotosensitive detector, said registering means further registering asecond representation of the distance between the starting point of thesecond scan and the point where the second scan is detected by saidphotosensitive detector, and said correction deflection signalgeneration means generates the correction deflection signal inaccordance with the relative values of said first and secondrepresentations.
 11. The apparatus of claim 10 wherein the correctiondeflection signal has an amplitude related to the difference between thevalues of the first and second representations.